This invention concerns foreign body rejection in mobile harvesters and, more particularly, rejection of non-frangible bodies such as stones or rocks in an axial flow rotary separator of the type which may be used in a combine harvester. For convenience, these undersirable foreign bodies will be referred to generically as stones.
Ingesting a stone may cause severe damage to internal members of a combine, especially high inertia portions such as the threshing mechanism. Control or rejection arrangements designed to limit the size or weight of stones reaching "critical" regions of the combine are well known. Practical considerations and harvesting economics dictate that some potentially damaging stones must be accepted into the gathering and feeding systems of the harvester but steps are taken to control or reject them before they reach critical processing areas of the machine.
Existing devices generally attempt to control or reject the stone either in the feeder house of the combine or, in conventional machines, no later than at the threshold of the concave, at the entry to the threshing zone. Releasable doors, set into the floor of the feeder house or concave threshold, may be associated with pressure sensitive or other stone detection devices calibrated and operable to permit the ejection from the crop material mat of stones exceeding acceptable limits. In another form of feeder house stone control, the floating of a lower portion of the feeder conveyor is restricted so that engagement of large stones by the (undershot) conveyor tends to jam the conveyor. A slip clutch in the conveyor drive system minimizes damage to the conveyor and its drive train.
Feeder house stone control arrangements of the types alluded to above are applicable to both so-called conventional combines and the more recently appearing so-called rotary combines (which include axial flow rotary separators). But all are of limited reliability and some are relatively complex and costly and may impose the inconveniences of resetting after each stone incident, or of frequent readjustment. No known devices take advantage of operating or functional characteristics peculiar to axial flow rotary separators.